Hi,
Efficiency of memory reclaim is recently one of the hot topics. (LRU splitting,

pageout throttling, etc...) I would like to contribute it and I made this patch.
In shrink_zone(), system can not return to user mode before it finishes to

search LRU list. IMHO, it is very wasteful, since the user processes stay

unnecessarily long time in shrink_zone() loop and application response time

becomes relatively bad. This patch changes shrink_zone() that it finishes memory

reclaim when it reclaims enough memory.
the conditions to end searching:
1. order of request page is 0

2. process is not kswapd.

3. satisfy the condition to return try_to_free_pages()

   # nr_reclaim > SWAP_CLUSTER_MAX
Signed-off-by: Takenori Nagano <t-nagano@ah.jp.nec.com>

Signed-off-by: Keiichi Kii <k-keiichi@bx.jp.nec.com>
---

diff -uprN linux-2.6.26-rc6.orig/mm/vmscan.c linux-2.6.26-rc6/mm/vmscan.c

--- linux-2.6.26-rc6.orig/mm/vmscan.c	2008-06-13 06:22:24.000000000 +0900

+++ linux-2.6.26-rc6/mm/vmscan.c	2008-06-20 15:05:03.492700863 +0900

@@ -1224,6 +1224,9 @@ static unsigned long shrink_zone(int pri

 			nr_reclaimed += shrink_inactive_list(nr_to_scan, zone,

 								sc);

 		}

+		if (nr_reclaimed > sc->swap_cluster_max && !sc->order

+						&& !current_is_kswapd())

+			break;

 	}
 	throttle_vm_writeout(sc->gfp_mask);
--

I have 3 question.
1. Do you have any performance number?

2. I think this patch advocate many try_to_free_pages() called is better than

   one try_to_free_page waste long time. right?

   and, why do you think so?

3. if this patch improve perfomance, I guess DEF_PRIORITY is

   too small on your machine.

   if DEF_PRIORITY is proportional to system memory, do your problem are solved?
--

I tested some, but I don't collect data.  :-(
I think user process is stopped long time on memory reclaim is not good.

It is enough for user process to reclaim memory is needed. We have kswapd memory
Your idea is so nice.  :-)

IMHO, it is not perfect if reclaimable memory is not on front.
Thanks,

  Takenori

--